Process for the manufacture of a triarylmethane compound

ABSTRACT

A PROCESS FOR THE MANUFACTURE OF A TRIAMINOTRIARYLMETHANE COMPRISING REACTING A DIAMINOBENZHYDROL SUCH AS MICHLER&#39;&#39;S HYDROL WITH AN OPTIONALLY SUBSTITUTED ARONATIC SECONDARY OR TERTIARY AMINE IN THE PRESENCE OF PHOSPHORIC ACID.

United States Patent "Ce $375,442

Patented Nov. 27, 1973 The substituents R, R R R R and R are most pref 3,775,442 erably methyl or ethyl radicals. Other substituents Which PROCESS FOR THE MANUFACTURE OF A may be present in rings A and B include alkyl, alkoxy and TRIARYLMETHAN COMPOUND halogen but it is preferred that said rings are unsubsti- Nigel Hughes, Manchester, England, assignor to Imperial tuted. X may be an optionally substituted 1,4-naphthylene ggmfg z fis ;g gfgigf i g f iggg residue but is preferably an optionally substituted 1,4- Claims priority, application h Britain, Aug. 27, 1970, phenylene resld ue. In addition to the NR R group other 41,24z/70 substituents which may be present on X mclude carboxy,

I t, (1 10% 11 10 sulpho, carboalkoxy, optionally substituted alkyl, carbam- Us, (1], 260-391 3 Cl i 10 oyl, cyano, nitro, hydroxy, acyloxy, acyl and halogen.

Compounds of Formula I which may be used in the process of the invention include 4,4'-bis(dimethylamino) ABSTRACT OF THE DISCLOSURE benzhydrol commonly known as Michlers hydrol. Exam A process for the manufacture of a triaminotriarylples of suitable amines of Formula II include N,N-dimethane comprising reacting a diaminobenzhydrol such 15 methylaniline, m-dimethylaminobenzene sulphonic acid, as Michlers hydrol with an optionally substituted arom-dimethylaminobenzoic acid, methyl m-dimethylamino matic secondary or tertiary amine in the presence of phosbenzoate, m-dimethylaminobenzonitrile, 3 carboxy-N- phoric acid. ethyl-a-naphthylamine and N-phenyl-a-naphthylamine.

Suitable amounts of phospheric acid for use in the This invention relates to a chemical process and more process Of the invention are usually in the range of from particularly to a process for the manufacture of com- 100% to 1000% by Weight based on the weight of repounds of th triarylmethane ri s actants. The reaction may convemently be carried out According to the invention there is provided a process at temperatures between 50 C. and 150 C. The process for the manufacture of a triarylmethane compound hav of the invention provides excellent yields of the triaryli th n al form la; methane compound. When the amine of Formula II is a relatively unreactive one the yields are much superior to R R2 those obtained in prior art processes where condensing agents other than phosphoric acid are used. This is par- R4 ticularly the case when the 1,4-arylene residue represented R by X carries one or more electron-Withdrawing substituents. Examples of such substituents include CN,

t COOR and -CONR R wherein R, R and R each represent hydrogen or optionally substituted lower alkyl.

wherein R and R each independently represents an op- The triarylmethane compounds obtained according to tionally substituted alkyl radical, R R and R each indethe process of the invention are leuco bases of triar 1 pendently represents an optionally substituted alkyl or methane dyes and may be converted into the said dyes by aryl radical, R represents a hydrogen atom or an optionventional method ally substituted allsyl radical, X represents a 1,4-arylene The invention is illustrated but not limited by the folresidue which may optionally be substituted and rings A lowing examples in which all parts and percentages are and B may optionally be further substituted, said process by weight: comprising reacting a benzhydrol of the formula: EXAMPLE 1 R m-Dimethylaminobenzoic acid (9.1 parts) and 4,4-bis (dimethylamino)benzhydrol (13.5 parts) are added to H stirred 80% phosphoric acid (75 parts) and the mixture is heated at 120 C. for 8 hours. The mixture is cooled (Formula to C., diluted with water (500 parts) and the pH of the resultant solution is raised to 5.0 by addition of Wherem R3 a d rings A d have e s gmfsodium hydroxide solution. The precipitated solid is colicallces Stated above, Wlth an amme of the fmmula! lected by filtration, washed with Water and dried in air.

50 19.0 parts of 2-[4,4'-bis(dimethylamino)benzhydryl]5- dimethylaminobenzoic acid having a melting point of 200 C. are thus obtained.

a (Formula II) Similarly, by condensing the compounds given in columns A and B of the following table, under the same wherein R R and X have the meanings stated above, in reaction conditions, the products given in column C are the presence of an effective amount of phosphoric acid. obtained.

Example A B O 2 4,4-bis(djmethylamino)benzhydrol. m-Diethylaminobenzoic aeid 2-%,4-bi s(dinethylamino)benzhydryl1-5-diethylaminoenzoie ac1 4 do W Ethyl m-dimethylaminobenzoate- Ethyl-2-[4,4-bis(dimethylamino)benzhydryH-fi-dimethylaminobenzoate.

6.. MW do 4-(N-ethy1amino)-2-naphthoic aeid 1-[4,4'-bis(dimethylamino)benzhydryl1-2-earboxy-4-(N- ethy1amino)-naphthalene.

7 4,4'-bis(dimethylamino)benzhydrol m-Diethylaminobenzoic acid 2-[%,4-bi s(dieghy1amino)benzhydryli-fi-diethylaminoenzoic aCl 8. 4,4'-bis(dimethylamino)-2,2- m-Dimethylaminobenzoie aeid..;. 2-[4,4-bis-(dimethylamino)2,2-diehlorobenzhydryl]-5- dichlorobenzhydrol. dimethylaminobenzoic acid.

3 I claim: 1. In a process for the manufacture of a triarylmethane compound having the general formula:

R OH R with an amine of the formula:

Rl HXN/ in the presence of a condensing agent, the improvement which comprises carrying out said reaction at C. to 150 C. using an effective amount of phosphoric acid as the condensing agent, the amount of phosphoric acid being from to 1000% by weight based on the weight of benzhydrol and amine.

2. A process as claimed in claim 1 wherein X carries a cyano, carboxy, carbcthoxy or carbamoyl radical.

3. A process as claimed in claim 1 wherein 4,4'-bis (dimethylamino)benzhydrol is reacted with m-dimethylaminobenzoic acid.

References Cited UNITED STATES PATENTS 3/1947 Adams 26039l 2/1964 Meuly 26O391 US. Cl. X.R. 260388 

